I built this to give my kids a close up observation of our backyard birds raising their young this Spring. It was a fun project we were able to do together and enjoy for many seasons ahead. It's really easy to build and requires only common shop tools. Here's how I did it.

Step 1: Tools and Supplies

Supplies

Any Common Birdhouse
Suction Cup Set

Tools

Table Saw, Miter Saw or Rotary Tool (used to cut off the back face of the birdhouse)
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Optional

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Step 2: Cut the Back Off

Use a table saw, rotary saw, or miter saw to cut off the back of the birdhouse. My table saw was able to rip through this in less then a minute.

Step 3: Add Suction to the Birdhouse

I used 4 suction cups to stick the birdhouse to my sons bedroom window. Hammer a small nail through the center of each suction cup. Then, nail each suction cup to the back of the birdhouse. In this picture you see only three cups on the birdhouse; however, the finished product actually has four. Three would have worked fine, but then I would have had a spare cup with no use.

Step 4: Stick to an Outside Window

Clean the surface of the window you intend on hanging the birdhouse. Now, firmly press the birdhouse to the desired location. There are a few extra tips to consider when hanging your birdhouse. You should at least know which birds frequent your backyard. Depending on the bird, their height and hole dimensions can vary greatly. Here are a few common dimensions from AmishGourds.